Description

   This routine initializes the thread attributes object specified
   by the attr argument with a set of default attribute values. A
   thread attributes object is used to specify the attributes of
   one or more threads when they are created. The attributes object
   created by this routine is used only in calls to the pthread_
   create() routine.

   The following routines change individual attributes of an
   initialized thread attributes object:

      pthread_attr_setdetachstate()
      pthread_attr_setguardsize()
      pthread_attr_setinheritsched()
      pthread_attr_setschedparam()
      pthread_attr_setschedpolicy()
      pthread_attr_setscope()
      pthread_attr_setstackaddr()
      pthread_attr_setstacksize()

   The attributes of the thread attributes object are initialized to
   default values. The default value of each attribute is discussed
   in the reference description for each routine previously listed.

   When a thread attributes object is used to create a thread,
   the object's attribute values determine the characteristics
   of the new thread. Thus, attributes objects act as additional
   arguments to thread creation. Changing the attributes of a
   thread attributes object does not affect any threads that were
   previously created using that attributes object.

   You can use the same thread attributes object in successive calls
   to pthread_create(), from any thread. (However, you cannot use
   the same value of the stack address attribute to create multiple
   threads that might run concurrently; threads cannot share a
   stack.) If more than one thread might change the attributes in
   a shared attributes object, your program must use a mutex to
   protect the integrity of the attributes object's contents.

   When you set the scheduling policy or scheduling parameters,
   or both, in a thread attributes object, you must disable
   scheduling inheritance if you want the scheduling attributes
   you set to be used at thread creation. To disable scheduling
   inheritance, before creating the new thread use the pthread_attr_
   setinheritsched() routine to specify the value PTHREAD_EXPLICIT_
   SCHED for the inherit argument.